From the recycled american CNC machine tool 1979 production year, PIA chips were extracted.
Marking was missing, but one of the chips was replaced in 1981 with the original mc6821.
Manufacturer not known. In my assembled computer and this chip, the reset passes normally. Corresponding characters appear on the screen. I can not verify the work of the keyboard, because I have not collected it yet.
Who knows about this white chip. Since white ceramics except in the production of AMD I have not met. The Internet is also silent.
PS> I am going to sell a couple if there is a demand.